Lapping machine



April 23, 1940. 2,198,377

H. w. DUNBAR Er 1.

LAPP'ING MACHINE Filed April 27, 193'! 4 Sheets-Sheet 1 2 5 I [-7 G. l 585 1 M an" 166 .52 20 56 70 HOWARD VV. DLJNBAF? 55 HERBERT 5. INDGE Ap 1940' H. w. DUNBAR El AL 8,377

LAPPING MAQHINE Filed April 27. 1957 4 Shets-Sheet 2 22a Z80 2 265 229 264 ,1 gas 275 57 o 281 27/ 2 awe/WW HOWARD W. DUNBAR 5 HERBER T S. INDG'E Alli] H. w. DUNBAR ET AL 2,193,377

LAPPING MACHINE v Filed April 27, 1937 4 Sheets-Sheet 3 HOWARD W. .ULJNBAR Z6] HERBERT 5.1'NI7sE l 1940- H. w. DUNBAR ET'AL ,198,377

LAPPING MACHINE Filed April 27, 1937 4 ShBBtS-SIIQGt 4 Fi 1 HOWARD DUNBAR HERBER T S. INDGE Patented Apr. 23, 1940 LAPPmG MACHINE Howard W. Dunbar, Worcester, and Herbert S.

Indge, Westboro,

Mara, assignors to Norton Company, Worcester, Mass a corporation of Massachusetts Application April 27, 1937, Serial No. 139,226

' 8 Claims.

The invention relates to abrasive machines and with regard to its more specific features to lapping machines.

, One object of the invention is to provide a through feed lapping machine capable of imparting a smooth and mirror finish to cylindrical work pieces such as rolls and the like. Another object of the invention is to smooth a ground work piece, removing grinding lines and substantlally eliminating surface undulations. Another object of the invention is to provide a lapping machine which will smooth and polish cylindrical objects so that, when mounted in bearings or the like, no initial period of wearing l in the parts is required. Another object of the invention is to provide a lapping machine for the finishing of automotive parts whereby automobiles and other machines may be constructed which do not require slow speed operation for a go preliminary period. Another object of the, in-

vention is to eliminate the ridges and valleys in a ground work piece. Another object of the invention is to provide a continuously operating lapping machine which automatically ejects the work piece and which produces highly polished work pieces. Another object of the invention is to provide a lapping machine which may be operated in several different manners to produce different lapping effects. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, and in the several steps and relation or order of each of said steps 33 to one or more of the others thereof, as will be exemplified in the structure to be hereinafter described, and the scope of the application of which will be indlcated ln the following claims.

In the accompanying drawings in which is shown one of various possible embodiments of g the mechanical features of this invention,

Figure 1 is a front elevation of a continuous lapping machine constructed according to the invention; Figure 2 is a horizontal sectional view on an enlarged scale, taken on the line 2-4 of Figure 1, showing the driving and controlling apparatus for the dressing carriage; Figure 3 is a fragmentary sectional view, on an enlarged scale, of the reciprocatory driving mechanism for the upper lapping wheel;

Figure 4 is a fragmentary end elevation, on an enlarged scale, of the reciprocatory driving mechanism for the upper lapping wheel; Figure 5 is an end view'of the machine, with certain parts broken away and with certain parts in section, looking from the right in Figure 1;

Figure 6 is a vertical sectional view, on an enlarged scale, taken on the line 6-6 of Figure 1, showing the driving and controlling apparatus I for the dressing carriage which is also shown in Figure 2;

Figure '7 is a detailed vertical sectional view of a self-aligning anchorage for the screw shaft for feeding vertically the slide for the upper lapping 0 wheel;

Figure 8 is a fragmentary plan view of part of the mechanism for reciprocating the upper lapping wheel;

Figure 9 is a plan view of the machine with 1 the column shown in cross section and the upper wheel removed;

Figure 10 is an end elevation, taken from the left-hand side of Figure 1, of the reciprocating mechanism for reciprocating the lower front lap- Q ping wheel;

Figure 11 is a vertical sectional view, on an enlarged scale, taken on the line ii-li of Figure 1, illustrating the brake for the upper wheel;

Figure 12 is a vertical sectional view, on an is enlarged scale, of the lower rear wheel and its mounting;

Figure 13 is a sectional view, taken on the line i3-i3 of Figure 12;

Figure 14 is a sectional view, taken on the line 30 "-44 of Figure 12.

Referring first to Figure 1, we provide a support or base 20 of sufficient size and strength to provide a firm foundation for the machine elements. Referring now to Figure 5, uprising 35 from the base 20 and suitably secured thereto or integrally formed therewith is a column 2i which, as better shown in Figure 9, has vertical ways 22 and 23. Still referring to Figures 5 and 9, a vertically movable slide 24 has ways 25 and 0 26 complementary to the ways 22 and 23 respectively and thus the slide 24 is mounted for vertical movement, and the area of the surfaces on the several ways is sufllcient to hold the slide 24 from any movement, lateral, torsional or 4,5 otherwise, excepting vertical movement which is controlled as hereinafter described.

Referring now to Figures 1 and 5, the base 20 has, in front of the column ii flat horizontalplane surfaces 28, 29 and 30, the surfaces 28 and so 30 being in the same horizontal plane and being separated from the surface 29 by reentrant inclined plane surfaces 3| and 32, all of said surfaces constituting ways for a. pair ofcarriages II and It shown in Figure 5. The carriages II 55 and 36 have cooperating dovetailed ways fitting the ways formed by the surfaces 28, 28, 34, 3| and 32 and are movable horizontally fore and aft of the machine, thatv is to say parallel to the plane of Figure 5. By means of adjustable supporting and journalling means which will be presently described, the carriages 35 and 36 respectively support elongated wheels 31 and 38 the characteristics of which will be more fully pointed out hereinafter. The'wheels 31 and 38 constitute supporting and rotating means for a work piece W being operated upon by the machine, which work piece is lapped by an upper wheel 4|]. The upper wheel 40 is supported by the slide 24. All three wheels 31, 38 and 40 may be abrasive wheels and, so faras certain features of the invention are "concerned, the lower wheel 31 not only supports but also laps the work pieces.

While so far as certain features of the invention are'concerned, the wheels 31, 38 and 40 may differ widely in composition, shape and structure, we prefer to use for all of them silicon carbide abrasive grain, preferably of fine grit size, for example from 180 to 500 grit size, bonded together with an organic bond, either a natural resin such as shellac, or one of the synthetic resins such as phenol formaldehyde, or vulcanized rubber. A preferred characteristic of all the Wheels is denseness of structure, that is to say lack of pore space. For reasons of economy of manufacture and also in order to vary the lapping action on the work piece as it moves through the machine, we prefer to build up each wheel 31,, 38 and 48 from a series of annuli. Preferably the wheels 31 and 40 are true cylinders, while the wheel 38 is a frusto cone modified slightly to a pseudosphere. Starting from right to left of the machine, in case the work piece is fed through in this direction, the first annulus of each wheel is preferably made from abrasive grain of 180 grit size. successively grit sizes 240, 320, 400 and 500 are used and as eight annuli are shown for each wheel, there may be pairs of any particular grit size. For example, inthe preferred formv of the invention, the last two wheels are of grit size 500, the next two adjacent are each of grit size 400, the next two adjacent are of grit size 320, thenfollows an annulus of grit size 240 and finally one of grit size 180. Thus, as a work piece travels through between the wheels, it is lapped at first by wheels having relatively coarse abrasive grains, and as it proceeds through, the machine the lapping action becomes finer and finer until finally a highly polished surface is produced. The particular arrangement, however, is illustrative only and many variations thereof can 'be made. Furthermore, it is to be understood that ple of the variation in grit size of abrasive material along the length of axis of the wheel by designating the grit size of each annulus with numera'ls marked thereon.

Considering now the mounting of the long cylindrical wheel 31 upon the carriage 35 and referring to Figures 1 and 5, uprising from the left-hand side of the carriage 35 is a journal support 4| which has a plain journal bearing for the spindle 42 of the wheel 31. The Journal support 4| is rigidly attached to the carriage 35 in any suitable manner. At the other side, namely the right-hand side of the carriage 35, is a dovetailed slideway 43 slidably supporting a journal member 45 having a plain journal bearing for the right-hand end of the spindle 42. Abrasive annuli forming the cylinder 31 are mounted upon a sleeve 41, which sleeve is suitably fastened to the shaft 42.

The mounting of all of the wheels 31, 38 and 40 is more clearly shown in the case of the wheel 38 in Figure 12. Referring to that figure, the wheel is made up of a plurality of annuli, which annuli have internal diameters substantially, the same as that of a sleeve upon which they are mounted. The sleeve 50 has a shoulder 5| at one end thereof and is threaded at the other end. A nut 53 and a washer 54 hold the abrasive annuli removably in place. The sleeve 50 slidably fits and is keyed to spindle shaft 55 which has a flange portion 56 locating the sleeve 50 in an axial direction. The sleeve 50 is retained in position by means of a nut 51 fitting a threaded portion of the spindle shaft 55. At the opposite ends of the shaft 55 are portions of reduced diameter 59 and 68 for the journaling of the shaft. The other two wheels 31 and 40 are mounted on their respective spindles 42 and 6| in the same manner as already described in the case of wheel 38. By assembling a plurality of annuli upon sleeves, which sleeves are removably mounted upon the wheel spindles, the substitution and replacement of abrasive annuli is facilitated and the plurality of annuli and each of the supporting sleeves may be dealt with as if it were a long integral abra sive cylinder.

Considering now the support for the upper wheel 40, and referring to Figures 1 and 5, the slide 24 has integrally secured thereto a large overhanging support 65 having on its under side a plane surface 66 to which is attached a depending journal member 61 journaling one end of the shaft 6|. The other end of the shaft 6| is journaled in a slidable depending journal member 1|) which is slidable on dovetailed ways 1! and 12 formed on a depending slideway l3 fastened to the plane surface 66 of the overhanging 82 passes through a nut portion 84 integral with the slide 8|. Slide 8| in turn has vertical ways 86 for the support of a vertical slide 81, the position of which is controlled by a screw 88 passing through a nut portion 89 of the slide 81, as 1 fully shown in Figures 12 and 14. The screw 88 is held to the slide 8| by a journal 90 and stud 9|.

By moving the slide 81 vertically, the wheel 38 may be skewed relative to the wheel 31. As the wheel 38 may be slightly conical and as the precise diameter thereof may vary from time to time or different wheels may be used, appropriate adjustment is effected by moving the slide 8| backwards or forwards. After the correct adjustment of these slides is achieved, they may be locked in position by tightening bolts 95 and 86 which tighten the slides against the ways, as clearly indicated in Figures 12 and 13.

tension I23 of the vertical slide 81.

To complete the adjustment, it may sometimes be desirable to elevate or lower the righthand side of the wheel 33. To that end, referring to Figures 5 and 12, the-slide 33 has an integral upward extension I33 having thereon slideway IIII supporting a vertically movable slide I32 which may be adjusted by means of a screw I33 'suitably anchored, as in "the case of the screw 38, and passing through a nut portion similar to the nut portion 33. As in the case with slide 31, the slide I32 may be locked in place by means of tightening bolts I33.

Referring now to Figures 12 and 14, in order that these adjustments may be made without interfering with the rotation of the wheel 33, the shaft 55 has secured upon the reduced portion 33 a sphere II3 by means of a key III and nuts I I2. Keyed to the reduced portion 33 is a sphere H5. The sphere U3 is secured between a pair of half journals I I3, II1 which are held together by bolts II 8. The lower half journal I" is fastened by means of bolts I13 to a horizontal ex- Similarly, the sphere I I5 is journaled between half journals I2I and I22 which are attached together and to a horizontal portion I23 of the vertical slide I32 in the same manner as already described in the case of the half journals H3, H1. The,

bearing surfaces of the journals H3, H1 and I2I, I22 are spherical and, therefore, the shaft 5 5 is not only journaled for rotation, but also may be moved angularly within limits without causing a binding.

The wheel 31 is adjustable as a whole fore and aft of the machine, being as aforesaid mounted upon the carriage 35 which is movable fore and aft of the'machine, as already described. Attached to the carriage 35 is a nut I through which extends ascrew shaft I23 controllable by,

a hand wheel I21. Similarly, the carriage 33 has attached thereto '9. depending nut I33 through which extends a screw shaft I3I controllable by a hand wheel I32 for moving the wheel 38 as a unit fore and aft of the machine. The wheel 43 may be moved in a vertical direction by moving the vertical slide 24. As shown in Figure 5, this may be done by hand or by power. The vertically movable slide 24 has a platform I35 upon which ismounted a motor I33, the armature shaft of which is coupled by a coupling I31 to a shaft I38 mounted in a journal I33 of a casing I43. Coupled to the shaft I33 by a coupling I is a shaft I42 extending to the front of the machine and upon the front end of which is secured a hand wheel I43 cooperating with a suitable scal I44.

In the casing I43 and upon the shaft I33 is a worm I45 meshing with a worm wheel I43 mounted on a cross shaft I41 suitably journaled in the casing I43. .Fastened to the shaft I41 is a worm I43 meshing with a worm wheel I43 formed integral with a nut I53 through which passes a vertical screw I5I. The vertical screw I5I is attached, as shown in detail in Figures 7 and 9, by means of a floating and self-aligning support I52 to the column 2|. A full description of the details of this self-aligning support is not necessary to an understanding of the present invention since any other manner of attachment may be utilized and the self-aligning support is provided to take care of imperfections or inequalities of machining'the parts. A full description thereof, however, will be found in copending application Serial No. 5,271 filed February 6, 1935.

Byenergizlng the motor I33 which is controlled by the switch I33. the slide 24 may be moved vertically at any time. Fine adjustments may better be made with the hand wheel I43.

We provide means for rotating the wheels 31 and 38 in the same angular direction and at the same angular velocity. Referring now to Figures l, 5 and 9, upon the outer ends of the spindles 42 and 55- we secure double grooved V pulleys I32 and I35, respectively. We provide an electric motor I33 secured to the base of the machine. The armature shaft I31 of this motor is coupled by a coupling I33 to a shaft'I33 suitably journaled in a casing I13. Upon the shaft I33 is fastened a worm "I which meshes with a worm wheel I12. Worm wheel I12 is fastened to a shaft I13 suitably journaled in the casing I13, and upon the outer end of the shaft I13 is secured a double grooved v pulley I14. A pair of belts I15 pass around the pulley I14 and around the pulleys I32 and I35 and furthermore around an idler pulley I13 joumaled to a bracket I11 attached to the machine frame.

We provide means to reciprocate the lower wheel 31 and further means to reciprocate the upper wheel 43. Each'of the wheels 31 and 43 is,

in this illustrative embodiment of the invention, a true cylindrical wheel. Dressing and truing of each of these wheels leaves them as true cylindrical wheels in contradistinction to the wheel 33 which may start as a cylinder or a frusto-cone, but which after truing or shaping by the wheel dressing apparatus hereinafter described, has the shape of a pseudosphere. So far as certain features of the invention are concerned, we might reciprocate one of the wheels 31 or 43 alone. We prefer, however, to reciprocate both of them. We further prefer to reciprocate them oppositely as the tendency of one to draw the work piece W axially in a given direction is thereby neutralized'by the other one. By reciprocating the wheels 31 and 43 in this manner, ridges on the workpiece W which were made by a previous grinding operation are substantially eliminated. Furthermore, as will more fully appear from the further description hereinafter, the action of this machine involves a true lapping action as an irregular rubbing action is achieved. So far as angular motion is concerned, the upper wheel 43 is the principal or sole lapping element, the lower wheels 31 and 33 being the driving or work rotating wheels. So far as rectilinear motion is concerned, each of the wheels 31 and 43 may be described as lapping wheels as each thereof has a surface action upon the work piece. The wheel 38, in this illustrative embodiment of the invention, is substantially solely a work supporting and rotating wheel.

Referring now to Figures 1 and 10, on the lefthand end of the shaft I13, which extends through the base of the machine as shown, is an eccentric block I83 having a slideway therein supporting a slide I3I, adjustment of which is controlled.by a screwl 82 to vary the eccentricity of a pin I83 secured to the slide I3I. A universal connection I84 is mounted on the pin I 33 and is pivotally connected to a link member I35. The link member I85 is adjustably connected by clamps I83 and I81 to a link member I88. The link member I33 is connected by means of a universal connection I33 to a bell crank lever I33 which is pivotally connected to a bracket I3I projecting from the journal support 4I. As shown in Figure 10, the

upper end of the bell crank I33 includes a fork I82 having shoes I98 engaging the grooves in a collar I 94 secured to the end of the spindle 42.

Rotation of shaft I13 produces an oscillating motion of the links I85, I88 which constitute in effect a connecting rod. The amplitude of oscillation is adjustable by means of the screw I82. This connecting rodv constituting the links I85, I88, which itself is adjustable as shown, produces an adjustable oscillation of the bell crank I90 which in turn produces an adjustable reciprocation of the spindle 42. It will be noted that spindle 42 is mounted in plain bearings and suflicient room is provided between the journal supports 4| and '45 for a reciprocation of considerable amplitude.

The upper wheel 40 is likewise mounted in plain bearings for its spindle 6i and with ample clearance for reciprocation and is reciprocated in like manner. Referring now to Figure 5, the rear end of the armature shaft I61 is connected by means of a coupling I99 to a shaft 200 journaled in a casing 201. Upon the shaft 200 is secured a worm 202 which meshes with a worm wheel 203 ioumaled in the casing 201. Referring now to Figure 3, the worm wheel 203 is fastened to a shaft 205 upon which is fastened a bevel gear 206 meshing with a bevel gear 201 which is journaled in a bracket 208 extending from the casing 201. A splined shaft 2I0- passes through the gear 201 which is broached to fit the shaft 2| 0. Referring now to Figures 3 and 5, the upper end of the fastened to shaft 2 l4 that is likewise journaled in the bracket 2. Referring'now to Figures 1, 4 and 9, fastened to the end of the shaft 2 opposite the bevel gear 213 is an eccentric block 220- l-having mounted therein a slide 22I adjustable by means of a screw 222, which slide 22I mounts an eccentric pin 223 on which is mounted a universal connection 224 connected to a link 225. By means of a pair of clamps 226 and 221, the link 225 is connected to a link 228. Link 225, clamps 226 and 221 and link 228 constitute an adjustable connecting rod, as in the case of link I85, clamps I86 and I81 and link I88. Connected to the link 228 is a universal connection 229, the other end of which is connected to a bell crank lever 230 pivoted at 23I to a bracket 232 extending downwardly from the overhanging support 65. The bell crank 230 has a forked portion 235 mounting shoes 233 which fit in a collar 234 secured to the right-hand end of the shaft 6|. Thus is the upper wheel adjustably reciprocated and by reason of the fact that both wheels 31 and 40 are reciprocated from the same main drive shaft I61, which is the armature shaft of the motor I66, and by further reason of the fact that the gearing is positive, the mechanism may be timed and preferably is timed so that the two wheels are reciprocated in opposite phase.

Considering'now the action of the upper wheel 40 and referring particularly to Figures 1 and 11, keyed to the shaft 61 is 'a brake drum24'0. A brake band 2 extends' around the drum 240, being anchored at one end to a block 242 and at the other end to a nut 243, and is controlled by hand wheel 245, and by means thereof the brake can be applied or loosened, as desired. The block 242 is mounted upon rods 246 extending laterally "from the journal bracket 61 so that the block brake 240 may flt with a sliding flt upon the shaft 8|, being, however, keyed thereto as already described by means of a key 241. The wheel 40 thus drags against the work piece or work pieces. The work piece is rotated by the lower wheels 31 and 38, and the upper wheel performs a lapping action by its slow rotation. In other words, the work piece rotates faster than the lapping wheel 48, and the work piece drives the lapping wheel 40. The action can be varied by tightening and loosening the brake. I

The wheels are dressed and trued from time to time and the wheel 38 is formed into a pseudosphere wheel by dressing apparatus fully described in copending-application Serial No. 5,271 filed February 6, 1935 and as described and claimed in application Serial No. 132,753 filed March 24, 1937 which is a division from said application Serial No. 5,271,

Referring now to Figure 9, at the front of the machine and attached to the base 20 is an apron 250. As better shown in Figure 6, the apron 250 has ways 25l, 25I supporting the slide 252 for movement in a horizontal direction. Between the ways 25I, 25I is a rack 253 which is secured to the apron 250. Meshing with the rack 253 is a small gear 254 mounted upon one end of a shaft 255 journaled in the slide 252. Fastened to the other end of the shaft 2551s a bevel gear 258 with which, as better shown in Figure 2, mesh a pair of bevel gears 251 and 258.

Referring now to Figure 1, an electric motor 260 is mounted upon a platform 26I connected to the slide 252. The motor 260 drives .by means of a belt 262 a pulley 263. As better shown in Figure 6, the pulley 263 is integral with a shaft 264 which is mounted in journals 265 and 266, the formerin a casing 261 which encloses the gears 256, 251 and 258, and the latter journal 266 being in the main part of the slide 252. Fixed to the shaft 264 is a worm 268 meshing with a worm wheeel 269.

Referring now to Figure 2, the worm wheel 269 is pinned to a shaft 210 on which are mounted the bevel gears 251 and 258. A sliding clutch collar 21I having teeth at both ends is keyed to the shaft 218 and adapted to engage clutch teeth formed on the inner ends of the bevel gears 251 and 258. Referring to Figures '2 and 6, a fork 215 engages the clutch collar 2, extending into a groove 216 thereof. The fork is pivotally con nected to an arm 218 which is pinned to a shaft 219, to the other end of which is pinned a hand lever 280. As shown in Figure 2, an operating rod 28l is connected to the upper end of the arm 218, being mounted on the pin 282 which pivotally connects the fork 215 to the arm 218. Referring now to Figures 1, 2 and 6, a rod 283 is pivotally connected to the manual operating lever 280. Rod 28l is positioned to contact a stationary dog 285 extending horizontally from the front side of the machine, while the rod 283 is positioned to contact a stationary dog 286 connected to the left-hand side of the apron 250.

When the motor 260 is energized, the slide 252 may be caused to traverse upon the ways 25I, 25l by swinging the operating lever 280 to the right or the left, thus engaging one or the other of the gears 251 or 258 with the shaft 210, thereby driving the gear 254 to traverse the slide or carriage 252. Upon reaching the end of its stroke, the slide or carriage 252 is automatically stopped by engagement of one or the other of the rods 28!, 283 with the dogs or stops 285, 286. respectively.

the dressing wheel standard 299 are slideways 29! supporting a vertically movable slide 292. By meansof a hand wheel 293 operating a screw 294 engaging a nut 295 secured to the slide 292, the

, slide 292 may be raised and lowered. The screw I 294 is held to the standard 299 by means of a thimble and collar 291, 299. Joumaled in the slide 292 is a spindle 299 supporting a dressing wheel 399. By means of a pulley 391, belt 392 and a pulley 393 driven by the motor 299, as well as idler pulley 394, the pulley 39l and, therefore, the spindle 299 is driven when the motor 299 is energized, thereby rotating the dressing wheel 399. As clearly shown in Figure 5, the dressing wheel 399 has a toric surface periphery. In other words, the wheel 399 is in the form of a disk with a toric periphery. As a result, when the totating wheel 399 is traversed in contact with each'of the wheels 31, 39 and 49, the wheels 31 and 49 are dressed to true cylindrical surfaces as their axes are parallel to the ways The wheel 38, however, is shaped to a pseudosphere such that a work piece may move along it in contact with it without distortion, the work piece being also in contact with the wheels 31 and 49.

The wheel 399 is rotated at a fairly high peripheral velocity while the wheels 31 and 38 rotate at a slow speed. The wheel 399 is traversed for dressing purposes very slowly so that all parts of the wheels 31 and 39 are contacted by the dressing wheel 399. For dressing purposes, the wheel 49 is also revolved although at other times it is only allowed to rotate under control of the brake mechanism described. Referring now to Figure 4, we provide a pulley 395 and double V belt 396 driven from a motor 391 and pulley 399 to rotate the wheel 49 for dressing purposesl The motor 391 may be supported upon any suitable part of the slide 24, as better shown in Figure 9.

Any type of work feeding troughs and work removing troughs may be used, such as those shown in copending application Serial No. 5,271 filed February 6, 1935. Exceptlng when the wheels are being dressed, the dressing instrumentalities are kept at the left-hand end of the machine, as shown in Figure 1. Preferably the work piece is moved from right to left in Figure 1 and under these conditions the wheels 31 and 39 revolve counterclockwise (Figure 5). The drag on the wheel 49 is, under such conditions, also counterclockwise. The wheels 31 and 49, because they are not skewed and because they are both cylinders, have no tendencyto move the work piece through the lapping throat, which may be 1 defined as the space between the three wheels 31,

39 and 49. On account of the skew or inclination of the wheel 39, however, the work piece is forced slowly through the lapping throat. With the inclination asshown in Figure 5 and the wheels rotating in a counterclockwise direction, the work piece will be moved from right to left (Figure 1), that is to say away from the observer in Figure 5.

We have found that an excellent finish can be achieved by the machine described and ridges and grinding lines are readily removed. The machine is adapted particularly for receiving work pieces that are already ground within close tolerances and under such conditions can act as.

order to produce pressure upon the work piece or work pieces, we locate the upper wheel 49 so that the lapping throat is slightly less in size than the work piece, by a matter of a few ten thousandths of an inch. The inevitable spring in theparts, by reason of the G shaped construction as clearly shown, causes separation enough to allow the work piece to enter and be lapped.

It has been pointed out that the wheels 31 and 49 are reciprocated oppositely. We prefer that the amplitude of reciprocation of each wheel shall be the same. By reciprocating themoppositely,

we mean that whenone wheel is in the righthand end of its stroke, the other one is at .the left-hand end thereof and vice versa. Since the reciprocating mechanism shown and described is positive in action and a direct connection exists between the bell cranks for reciprocating the wheels respectively, it follows that the wheels this feature,-especially' when the wheel 31 is also an abrasive wheel, the tendency to move the work piece axially due to movement of one wheel is neutralized or opposed by the other one. However, each wheel, by its longitudinal or reciprocating motion, abrades the work piece in the direction of the axis thereof, and consequently effectively laps the work piece. The relative motion between the work piece and the various wheels is highly complex and consists of a compound of relative angular and relative axial motions. Furthermore, as the diameter of the work piece is not necessarily equally divisible into the diameters of the several wheels, and will not be for long owing to wear of and dressing of the wheels, and even in case it is on account of the slippage between work piece and wheels, the

\ abrasive action of the wheels upon the work piece is not cyclically repeated and consequently every portion of the work piece receives an irregular abrasion which is found to be a highly effective lapping action.

With regard to the relations of the three wheels which form a work receiving throat, it will be seen that each wheel is located between the other two wheels and to one side of lines connecting the axes of the other two wheels. In the case of the two wheels 31 and 49, these lines connecting the axes form a plane. In the case of any pair of wheels including the wheel 39, these lines do not form a plane but nevertheless define a surface. and the third wheel is always to one side of said surface and between the two given wheels. With such a relationship of wheels, two of them being parallel and the third being dressed as herein described, a work piece receiving throat is formed in which the work piece is contacted at three distinct lines.

It will thus be seen that there has been provided by this invention apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As many possible embodiments may be made of the above invention and as many changes might be made in the embodiment above set forth, it is to be understood that all matter vhereinbefo-re set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

We claim: I

1. In an abrading machine, a first wheel cylindrical in shape, means for rotating said first wheel, means for reciprocating said first wheel axially, a second wheel pseudospherical in shape, means for rotating said second wheel in the same angular direction as and at the same angular velocity as said first wheel, a third wheel cylindrical in shape and formed of abrasive material, and means for reciprocating said third wheel axially at the same rate and amplitude as the first wheel but in a phase always opposite to that of the first wheel, the three wheels forming a work throat to hold a work piece between them, the work piece being rotated by the first and second wheels and fed axially by the second'wheel which is skewed with respect to the path 01' travel of the work piece, and the work piece being abraded by. the third wheel which is driven by the work piece.

2. In an abrading machine, a first wheel cylindrical in shape, means for rotating said first wheel, a second wheel pseudospherical in shape and slightly skewed with respect to said first wheel, means for rotating said second wheel in the same angular direction as said first wheel,

a third wheel cylindrical in shape and formed of abrasive material, and means for reciprocating axially both of said cylindrical wheels at equal and opposite rates. I

3. In an abrading machine, a pair of wheel positioned to support a work piece, means to totate said wheels in the same angular direction, a third rotatable wheel between the wheelsof said pair and outside of lines connecting the axes of the wheels of said pair and adapted to engage a work piece supported and rotated by the said pair, said third wheel being an abrasive wheel, all of the wheels rotating during operation of the machine, and two of the wheels having parallel axes, and means for retarding said third wheel, thuscausing it to drag against the work piece .which is driving the third wheel,

, thereby producing a fine lapping action and distributing the wear over all parts of the third wheel.

4. In an abrading machine, a pair of wheels positioned to support a work piece, means to rotate said wheels in the same angular direction, one of said wheels being a pseudosphere and having its axis skewed relative to the path of travel of the work piece, whereby said pair of wheels not only support and rotate a work piece but also feed it axially, a thirdrotatable wheel between the wheels of said pair and to one side of lines connecting the axes of the wheels of said pair, the third wheel being an abrasive wheel, all of the wheels rotating during operation of the machine, and means for reciprocating one 01' the wheels axially.

5. In an abrading machine, a pair of wheels positioned to support a work piece, means to rotate'said wheels in the same angular direction, one of said wheels being a pseudosphere and having its axis skewed relative to the path of travel of the work piece, whereby said pair of wheels not only support and rotate a work piece but also feed it axially, a third rotatable wheel between the wheels of said pair and to one side of lines connecting the axes oi the wheels of said pair, the third wheel being an abrasive wheel, all of the wheels rotating during operation of the machine, and means for reciprocating two of the wheels axially. w l

6.. In an abrading machine, a pair of wheels positioned to support a work piece, means to rotate said wheels in the same angular direction, a third rotatable wheel between the wheels 01' said the wheels 01' said pair and adapted to engage a work piece supported and rotated by the said pair, said third wheel being an abrasive wheel, all

of the wheels rotating during operation of the 30 pair and outside of lines connecting the axes of drical in shape, means for rotating said first wheeLa second wheel pseudospherical in shape and slightly skewed with respect to said first wheel, means for rotating said second wheel in the same angular direction as said first wheel,

.wheel being driven by the work piece against action of the brake.

8., In an abrading machine, a first wheel cy-,

lindrical in shape, means for rotating said first wheel, a second wheel pseudospherical'in shape and slightly skewed with respect to said first wheel,- means for rotating said second wheel in the same angular direction as said first wheel,

a third rotatable wheel cylindrical in shape and formed of sections of abrasive material of different grit sizes, and means for reciprocating one of said cylindrical wheels axially, all of the wheels rotating during operation of the machine.

HOWARD W. DUNBAR. HERB ERT S. INDGE. 

